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## Review of Descriptive Geometry

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**Review of Descriptive Geometry**Lecture 10 Autumn Quarter**Topics For Today**• Quiz – CAEG – AutoCAD • Drawing Number 18 is due • Lab report due on Wednesday at the beginning of the lab period • Lab Report – Follow the example, calc. % at each speed, graph in %, use two mph groupings (24 and 25 – avg 24.5) or three mph groupings (24 thru 26 -- avg 25) • Descriptive Geometry • Read BTG Chapter 11 Autumn Quarter**Review from Monday**• Lines and planes extend to infinity while we work with a small portion which we define. • Lines and planes can be extended. • Dihedral angle – The angle between two planes – smaller of the two. It can be found by finding the line of intersection and looking at the line of intersection as a point. • Angle between a line and plane – This requires a view in which the plane is an edge and the line is true length. Autumn Quarter**Review from Monday**• Downloaded a blank3d template – 4 viewports, 3D construction, world coordinates, cursor tracking – world • Layout mode – Transferring the model to paper – tab at the bottom of screen • The layout and the model or construction mode are all part of one file. Autumn Quarter**Review from Monday**• VIEW – Using UCS menu • 3 UCS + plan (enter) (enter) – gives true size of plane • Z UCS + plan (enter) (enter) – gives end view of line which could provide edge view of a plane or a dihedral angle Autumn Quarter**Construction Hint**• When you have created a line and then look down the line so the line appears as a point, it disappears in AutoCAD. When you know this is going to happen, place a point (+) at each end of the line. • Save often but don’t overwrite the blank3D file. Autumn Quarter**Key to Descriptive Geometry**Top Know the location of the origin (0,0,0) Front Right Side Autumn Quarter**Angle between a line and plane**• Required – a view where the line is true length and the plane is an edge • In pencil construction, three auxiliary views are required 1) edge view of plane 2) true size of plane 3) edge view of plane and true length of line • Using the UCS menu and the PLAN command shortens the process Autumn Quarter**Today’s Assignment**• Dwg 19 – SGAC-4-1 • Angle between a line and a plane in space • Due at end of class today • Read Handout – steps for solving problems in AutoCAD are provided • Dwg 20 – SGAC-4-2 • Dihedral Angles • Due at beginning of next lecture • Read Handout – steps for solving problems in AutoCAD are provide Autumn Quarter